Contact breaker of ignition systems for internal-combustion engines



Aug. 18, 1953 L. DELORME 2,649,515

CONTACT BREAKER OF IGNITION SYSTEMS F OR INTERNAL-COMBUSTION ENGINESFiled July 9, 1951 2 Sheets-Sheet l Fig .3.

INvENTo/P 3 Lac/EN Dem/9 5 Aug. 18, 1953 DELORME 2,649,515

CONTACT BREAKER 0F IGNITION SYSTEMS FOR INTERNAL-COMBUSTION ENGINESFiled July 9, 1951 2 Sheets-Sheet 2 IN 111-: N ToR L Lia E ,v D ELMQAAEPatented Aug. 18, 1953 CONTACTBREAKER OF IGNITION SYSTEMS FORINTERNAL-COMBUSTION ENGINES Lucien Delorme, Paris, France, assignor toSociete Anonyme dite: Etablissements Ducellier, Paris,

France Application July 9, 1951, Serial No. 235,861 In France July 8,1950 3 Claims.

This invention relates to ignition systems for internal combustionengines and more particularly to improvements in contact breakersmounted in the primary circuit of ignition systems, either of the H.-T.coil or magneto type, applicable more especially to those casesrequiring a relatively high frequency of contact breaks, for example20,000 per minute.

The chief troubl in designing a contactbreaker in view of obtaining sucha high number of breaks is to obtain constant opening and closing timeintervals and, above all, to avoid the bouncing eifect generallyproduced at high speed when the contacts close.

This bouncing effect is caused by the impact of the movable contactagainst the fixed contact which brings about a momentary deformation ofthe arm carrying the movable contact on the one hand and of the membersupporting the fixed contact on the other hand. Both parts resume theiroriginal position with a force depending on the inertia and speed of thearm at the instant in which the impact occurs. When this force exceedsthat of the contact arm spring the contacts are opened. By increasingthe speed the same phenomenon may occur several times during eachclosing period of the contact-breaker.

In the case of H.-T. coil or battery ignition the consequence of thisbouncing effect is to reduce the time for setting up a current flowthrough the coil and therefore to step down its electrical energy. Inthe case of magneto ignition the bouncing eifect set up in thecontact-breaker may produce ill-timed ignition sparks.

One remedy to the drawbacks set forth hereabove is to reduce the inertiaof the contact arm or increasing the spring pressure, but mechanicaldifficulties or an excessive wear in the contactbreakers militateagainst this solution.

Now, according to this invention, a satisfactory answer to this problemis obtained by interposing a rubber pad between the fixed contact andits supporting member. This rubber pad exerts a shock-absorbing actionby damping out part of the energy spent in the closing impact and willresume its original position only at a relatively low speed. Then, theinertia of the contact arm is too low to overcome the pressure of thecontact spring and any rebound is avoided. The mechanical efiiciency ofthe contacts is improved and the noise substantially reduced.

The afiixed drawings forming part of this specification illustratediagrammatically by way of example one possible embodiment of theinvention, with the understanding, however, that the 2 invention is notconfined to any strict conformity with the showing of the drawings butmay be changed or modified so long as such changes or modifications markno material departure from the salient features of the invention asexpressed in the appended claims.

In the drawings:

Fig. 1 is a plane view of the contact-breaker.

Fig. 2 is a fragmentary side view showing the fixed contact with itssupporting member.

Fig. 3 is another fragmentary view of the fixed contact mounting.

Figs. 4 to 6 illustrate a practical embodiment of th invention wherein:

Fig. 4 is a plane view of the assembly;

Fig. 5 a side view of the fixed contact mounting, and

Fig. 6 an elevational view at a greater scale of the movable contactmounting.

Referring now to the drawings and firstly to the diagrammaticalembodiment of Figs. 1-3, the engine-driven cam I actuates a contact-arm2 through a cam-follower 3. The arm 2 carrying the movable contact 6 atits free end is pivotally mounted on a pin 4 and urged towards the cam lby a leaf spring 5. The movable contact 6 registers with a fixed contact1 fast with a small plate 8.

A supporting member 9 is adjustably mounted on a plate H). A rubber padII is interposed between the small plate 8 and the supporting member 9and cemented thereto through known methods. A strip 52 of flexible metalensures the electric connection between contact I and support 9.

In the modified embodiment of Figs. 4-6 the fixed contact 1 is fast withan arm 8 covered completely with a sheath of elastic material such asrubber. This arm 8 passes across a rubber pad H, in which it may beembedded by molding, so that the fixed contact is mounted in a resilientmanner while being electrically insulated from its supporting member.Thus, the vibration of the fixed contact 1 is damped out in asatisfactory manner, particularly when it is struck by the movablecontact 6, so that the latter will be prevented from bouncing. Therubber pad II is carried by a U-shaped bracket in which it is clamped.In the construction shown, the rubber pad H is slightly compressed bythe resilient force of a spring 5 acting upon the arm 2 carrying themovable contact so that when the contacts open the fixed contact I mayfollow to a certain extent the movable contact 6 whereby suitableclosing time conditions may be obtained.

Besides, when the contacts close the kinetic energy of the movablecontact is absorbed by the rubber pad I I and thus any tendency tobouncing is eliminated. In fact, the rubber material used as a supportnot only acts as a resilient member permitting a slight backwardmovement of the hitherto rigid fixed contact, but also as avibration-absorbing dash pot. By way of example, it may be indicatedthat a rubber material having a Shore hardness of 50i5is the mostsuitable for the purpose specified.

In order to reduce the inertia of the arm 2 and therefore suppress thebouncing effect caused thereby, the cam-follower 3 is mounted separatelyfrom this arm at one end 16 of a lever I! fulcrumed about a fixed pin I8and operatively connected with its opposite end I9 to a push rod 20 fastwith the movable centre of a diaphragm 2| subjected to a vacuum varyingin direct ratio with the engine speed. Under the best ignitionconditions, it is necessary that the engine acceleration and thereforethe increase in current breaks per time unit be accompanied by acorresponding increase in the dwell, that is the ratio of the contactclosing time to the total time of a cycle. For this purpose, the camfollower 3 is moved in a direction adapted to reduce the open contacttime and therefore increase the closed contact time with the increasingR. P. M. value.

The suppression of the bouncing effect is promoted by the fact that thearm carrying the movable contact is fixed with a leaf spring 13 of theimproved contact arm assembly of this invention. This spring Iconstantly bears against the suitably bent end of an arm 14, owing tothe resilient pressure of an auxiliary spring 15. With this arrangementthe conventional pivotal mounting of the contact arm which is a sourceof friction counteracted by a spring may be dispensed with. The assemblyconsisting of spring [3, counterspring l5 and arm 14 may be secured bymeans of a screw 22.

This reduction in the inertia of the contact arm and the suppression ofthe detrimental bouncing effect make it possible to reduce the contactpressure exerted by the spring 5 and therefore the pressure of the camfollower 3 on the cam I, thereby lessening the risks of shivering thecontact points at the impact and the wear of parts in frictionalengagement.

The face of cam follower 3 which engages the contact arm 2 is slightlycurved so as to work with, and distribute Wear over its entire surface,taking into consideration the circular path described by the camfollower during its operation.

The opposite face of cam follower 3 engaging the cam face proper iswedge-shaped in order to reduce to a minimum the lifting time, which isthe open-contact time, of the cam follower 3 on each projection of camI.

What I claim is:

1. A contact-breaker for ignition system comprising a supporting member,a rubber cushion carried by said supporting member, a fixed contact, anarm carrying said fixed contact, said arm passing through said rubbercushion without touching said supporting member, and a movable contactcooperating with said fixed contact.

2. A contact-breaker for engine ignition system comprising a supportingmember, a rubber cushion carried by said supporting member, a fixedcontact, an arm carrying said fixed contact, said arm passing throughsaid rubber cushion with- V V out touching said supporting member, arocking lever, a movable contact carried by said rocking lever andcooperating with said fixed contact, a rotary cam, a follower adapted totransmit the successive contact-breaking thrusts from said cam to saidrocking lever, a pivotally mounted arm, means adapted to move saidpivotally mounted arm inaccordance with the conditions of operation ofthe engine, and a pin mounted on said pivotally mounted arm and adaptedto act as a fulcrum to said follower between said cam and said rockinglever.

3. A contact-breaker for ignition system, comprising a supportingmember, a rubber cushion carried by said supporting member, a fixedcontact, an arm carrying said fixed contact, said arm passing throughsaid rubber cushion without touching said supporting member, a movablecontact cooperating with said fixed contact, a thin resilient bladehaving one stationary end and carrying said movable contact on the otherend, a fixed bearing member mounted in the vicinity of said stationaryend of said blade, a spring member adapted to urge said resilient bladeagainst said bearing member, and another spring member acting upon saidresilient blade between said fixed bearing member and said movablecontact, and urging said elastic blade in a direction such as to causesaid movable contact to engage said fixed contact.

LUCIEN DELORME.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,884,457 Wilkins Oct. 25, 1932 2,040,106 Rose May 12, 19362,348,896 Gibson May 16, 1944 2,471,318 Fitzsimmons May 24, 1949

